WASHINGTON — The acting administrator of NASA told Congress Thursday that some of the cost overruns besetting the space agency stem from counterfeit parts inadvertently installed on space craft.

“We find out late they are counterfeit parts,’” Christopher Scolese, the space agency’s acting administrator, told a House Science and Technology subcommittee. “We find out about it while sitting atop a rocket or, worse, find out about it in space.”

NASA has been trying to weed out counterfeit parts for years, Scolese said.

But the problem has been growing, with foreign firms and counterfeiters manufacturing equipment that ends up in NASA’s supply chain, Scolese told reporters after the session.

Most recently, he said, NASA personnel detected an unspecified counterfeit part on the Kepler spacecraft “a couple of months ago.” The discovery potentially contributed to a nine-month delay in launching the unmanned probe, which is designed to discover earth-like planets in the Milky Way Galaxy.

The counterfeit part was replaced on the spacecraft, which is scheduled for launch today, he said.

The Government Accountability Office advised the committee before Scolese’s testimony that the Kepler project had suffered a 20 percent cost overrun, which had driven the project’s total costs up to $595 million. But GAO investigators did not raise the problem of counterfeit parts.

The Kepler probe was one of 10 of NASA’s $250 million plus projects found by a GAO audit to have run over cost and over deadline. Investigators said average development costs alone had increased 13 percent and average launch delays stood at 11 months.

Counterfeiting has become a way of life around the world . The federal government estimates that trade in counterfeit items has skyrocketed from $5.5 billion in 1982 to $600 billion in 2008, accounting for up to 7 percent of world trade.

Bloomberg News Service reported that parts with stolen manufacturer markings have been found by NASA personnel and aerospace industry officials. Some of the counterfeit equipment includes aerospace components embossed with logos from top-flight aerospace manufacturers and sold at premium prices.